Online and Offline Calculators
Multiple Calculator Sites
Adam One comprehensive site with info from aerodynamics, design and guidance to good calculators for most things - http://adamone.rchomepage.com/
(aerodynamics, trainer design, equations, airfoil simulator, electrics calculator)
Electric Power Systems Calculators
Adam One - Comprehensive calc with plots - http://adamone.rchomepage.com/calc_motor.htm
DMA web calculator (not accurate?) - http://brantuas.com/ezcalc/dma1.asp
MotoCalc (commercial, standalone program) - http://www.motocalc.com/
RCgroups mega-list of calculators - http://www.rcgroups.com/forums/showthread.php?t=606703
Motor databases
Sources for Equations
Full propellor equations including graphs of Ct and Cp variation with pitch and model velocity - http://www.dc-rc.org/pdf/Model%20Propellers%20Article.pdf
Equations for electrical drive systems (batteries, ESCs and motors) - http://www.rcgroups.com/forums/showthread.php?t=185271
Spreadsheets
power, electric and model calculations - prop-power-calculator+.xls